Diaphragm



P. E. BU-TOW.

DIAPHRAGM.

'APPUC'ATION FILED MAY 5,1917. 1 1,334,435. Patented Mar. 23,1920.

88 mvron' W/T NE E8 I 5 Z;

A TTOR/VEYS sweetest quality,

UNITED STATES PATENT OFFICE.

PAUL E. BUTOW, OF BROOKLYN, NEW YORK.

DIAPHRAGM.

Specification of Letters llatent.

Patented Mar. 23, 1920.

Application filed May 5, 1917. Serial 1%. 166,531.

This invention relates to sound recording and reproducing machines and has particular reference to the construction of the sound boxes or reproducers of such machines,-and by the term sound boxes, as used herein, I mean to cover any analogous device for use on any kind of'sound recording or reproducing mechanism.

Amon the objects of the invention is to specifica ly improve the construction of the diaphragm whereby it is expedient to record and reproduce the tones of the human voice or other familiar sounds in the most faithful manner.

Another object of the invention is to produce a diaphragm for sound boxes in a novel and peculiar manner whereby, in con-.

nection with musical productions, the tones produced are of the fullest, clearest and as well as being practically exact reproductions of the original tones.

With the foregoing and other objects in view the invention consists in the-arrangement and combination of parts hereinafter described and claimed, and while the invention is not restricted to the exact details of construction disclosed or suggested herein, still for the purpose of illustrating a practical embodiment thereof reference is had to the accompanying drawings, in which like reference characters designate the same parts in the several views, and in which Figure 1 is a side elevation of my improved device showing a stylus and stylus bar in connection therewith; and

Fig. 2 is a vertical transverse section of the same on the line 22.

Referring now more particularly to the drawings I show a sound box comprising a shell 10 of any suitable rigid material, the main portion of which is hell shaped or curved preferably in an ogee curve all the way from the short cylindrical rim 11 into the coupling neck 12. As a sound box is ordinarily made and used it is of a flat nature with a more or less abrupt shoulder or ofi'set between the flange or mouth portion where the diaphragm is connected to the restricted shank or'neck portion, the result hemg that the tones orlginating in the diaphragm are seriously disturbed or broken in their movement from the diaphragm to the neck and tone'arm to which the sound box is connected. By reference to Fig. 2 therefore it "wlll be appreciated that by providing the gracefully curved interior of the shell of the sound box without sharp angles or shoulders the tones from the diaphragm will pass without material damage or obstruction mto and through the tone arm for delivery from the machine. 7

As a result of long experiments and experience in this art I have discovered that sound box diaphragms may advantageously be made of metal, if they can be formed thin enough and of uniform thickness. I

have discovered furthermore that it is practically impossible for a diaphragm to be made of metal thin enough for best results so as to maintain its perfect integrity, by rolling or stamping. a

According to my improvement therefore I provide a diaphragm 13 of thin spun metal of uniform thickness which, by way of example should be about .002 of an inch thick or less, and the metal I prefer. to use for this purpose which I have foundto be preemi nently successful is a soft quality of aluminum. As shown best in Fig. 2 the sheet or disk of metal is provided with a plurality of concentric convolutions or corrugations 14, 1-5 and 16 at its central portion whilethe outer rim portion is left flat as indicated at 17. The radius of the flat. portion is indicated as approximately fi' that of the corrugated portion. It will be noted also that the crests of theconvolutions project in opposite directions or on opposite sides ofthe central plane of the flat portion 17. 1 The periphery of the diaphragm is preferably gripped between two soft gaskets 18 and held in place by a spanner ring 19-.within the short cylindrical rim portion ll ofthe.

box.

The diaphragm as thus'far described has been found in practice to be exceedingly sat-' isfactory but "because of its extreme thinness has been found somewhat delicate to manip ulate. I therefore. provide some suitable reinforcement means for the central portion to which the stylus bar 20 is connected in the usual manner. The reinforcement means that I prefer to employ comprises a'small thin disk of celluloid 21 or'22 secured on either or both of the faces of the central portion of the diaphragrmthe securing being with each other or reach radially to about the crest of the second convolution 1 5 leav.- ing one of the. convolutions and the fiat portion of the diaphragm ofsingle minimum thickness. w

The formation of a diaphragm'of spun metal instead of rolling, stamping or otherwise forming them, possesses numerous advantages, among Which may be noted the "following:

. As above premised it is essential for the best quality reproduction of musical tones or for the most faithful reproduction of the human voice or other familiar sounds that the metal diaphragm be extremely thin.

Furthermore the texture of the metal, While" being exceedingly thin, Ought to be homogeneous and unbroken throughout. In other experience in the Working of thin metals I I Words there should be no parts or spots that are shattered, ragged or broken. -From my am convinced that there is no practical Way "of forming a resonant metal thin enough for the practical purposes of my improved in a uniform manner adapting them to the creation or formation of an extremely thin and uniform sheet.

' than celluloid may be used forthis purpose.

For instance I may form them of spun aluminumsimilarly to the formation of the -main portion of the diaphragm. .To secure the best results I have discovered that the total thickness of. the reinforced portion should not exceed approximately .004 of an inch, or twice the thickness of the main diaphragm.

I claim: A diaphragm for sound boxes comprising a thin sheet of spun aluminum.

PAUL E. BUTOW. 

